Principal Investigator

Jorge Sarmiento

At a Glance

Innovative float technology and high-resolution modeling are dramatically improving our view of the harsh and remote Southern Ocean.

 

Research Highlight

The new Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project combines cutting edge robotic float technology with high-resolution earth system modeling to expand our understanding of the Southern Ocean. Headed by Jorge Sarmiento of CMI’s Carbon Science Group and funded by the National Science Foundation, SOCCOM involves 25 researchers at 13 institutions around the U.S. and has an operating budget of $21 million over six years. The impetus for the project comes primarily from modeling research, including key studies carried out by the Sarmiento Group with CMI support, that suggests the Southern Ocean surrounding Antarctica plays a very important role in the planet’s carbon and climate cycles. Such theoretical studies indicate that

  • the Southern Ocean accounts for half of the planetary ocean uptake of anthropogenic carbon from the atmosphere1 and the majority of its uptake of heat (Sarmiento group analysis of the Fifth Coupled Model Intercomparison Project, CMIP 5; Refs. 2,3);
  • Southern Ocean upwelling delivers nutrients to lower latitude surface waters that are critical for ocean ecosystems around the world4,5; and
  • the impacts of ocean acidification from rising carbon dioxide (CO2) are projected to be most severe in the Southern Ocean, approaching ecosystem tipping points within a few decades6,7.

Until now, the biogeochemical (BGC) observations needed to test these model-based hypotheses have been sparse due to the harsh environment limiting access to the region by research vessels, particularly during the Southern hemisphere winter. To escape the limitations of ship-based measurements, the SOCCOM project is taking advantage of Argo autonomous float technology, which has already been widely deployed throughout the world’s oceans. SOCCOM scientists have augmented conventional robotic Argo floats (which measure ocean temperature and salinity) with newly developed biogeochemical sensors to measure carbon (indirectly determined by measuring pH), nitrate nutrients, and oxygen (see Figure 1.4.1). SOCCOM is the world’s first large-scale BGC Argo deployment and will increase the number of biogeochemical measurements made monthly in the Southern Ocean by a factor of 10-30 (with the higher increase in the Southern Hemisphere winter, when observations are scarcest).

Figure 1.4.1. Loading (inset) and deployment of a BGC Argo robotic float. (Inset photo courtesy of Hannah Zanowski, Princeton University. Outset photo courtesy of Annie Wong, University of Washington.)

A total of 200 floats are planned for deployment over the six-year term of the project. Since the spring of 2014, the SOCCOM team has deployed 24 BGC floats via two Southern Ocean cruises that sailed from Hobart, Tasmania and Cape Town, South Africa. Figure 1.4.2 shows a snapshot of pH provided by measurements taken along the trajectory of the Hobart-based GO-SHIP repeat hydrography cruise P16S (angled axis). The blue low pH water in the lower waters of the southernmost float is due to upwelling of deep water rich in dissolved inorganic carbon from decomposition of organic matter. The red high pH water in the surface ocean is due to low dissolved inorganic carbon from biological uptake. The deepening of this high pH water in Float 9095 is due to a combination of seasonal biological uptake, and the horizontal movement of this float across the so-called Polar Front which marks a boundary between waters with different properties. These floats are now complementing cruise data with unprecedented continuous monitoring of pH over time; the floats are providing the first annual record of the combined chemical and biological changes over broad regions of the Southern Ocean, and analysis of the newly collected data is underway.

Data from the floats are being made available to the public in real time at the SOCCOM website (http://soccom.princeton.edu) and will also be incorporated into the global Argo data system to provide easy access to researchers around the world. The project will also transfer sensor technology to commercial float developers and will work to ensure that the findings of the SOCCOM project reach the widest possible audience, including policymakers and the general public.

Several more BGC floats will be deployed this spring on cruises from Argentina and Tasmania, and the SOCCOM team is currently working with collaborators to organize the deployment of 37 floats to be built in 2015. The remainder of the floats will be launched between now and 2020. Combined with high-resolution modeling carried out under the project, SOCCOM’s leading-edge observations will help researchers better understand the inner workings of the Southern Ocean and its current impacts on Earth’s climate and biosphere. Predictive model simulations carried out under SOCCOM will also help researchers anticipate how changes in the Southern Ocean will impact global climate in the future.

Figure 1.4.2. pH measurements collected by BGC floats at three southern latitudes, launched from a GO-SHIP cruise along the south to north P16S cruise track. The map shows the south to north P16S cruise track as well as the locations of measurements made by BGC floats 9092, 9095, 9254, which are denoted by the black, green, and yellow dots, respectively. The vertical section cutting diagonally across the figure is pH measured at depths ranging from 0-1000 m, collected along the ship track at the time the floats were deployed. The vertical sections projecting out to the right show the time history of pH from BGC floats 9092, 9095, 9254 between April 2014 and January 2015. Figure courtesy of Ken Johnson, Monterey Bay Aquarium Research Institute (MBARI).

 

References

  1. Gruber, N., M. Gloor, S. E. Mikaloff Fletcher, S. Dutkiewicz, M. Follows, S. C. Doney, M. Gerber, A. R. Jacobson, K. Lindsay, D. Menemenlis, A. Mouchet, S. A. Mueller, J. L. Sarmiento, and T. Takahashi, 2009. Oceanic sources and sinks for atmospheric CO2. Glob. Biogeochem. Cycles, 23: GB1005. doi:10.1029/2008GB003349.
  2. Frölicher, T. L., M. Winton, and J. L. Sarmiento, 2014. Continued global warming after CO2 emissions stoppage. Nat. Clim. Chang., 4(1): 40-44.doi:10.1038/nclimate2060.
  3. Levitus, S., J. I. Antonov, T. P. Boyer, O. K. Baranova, H. E. Garcia, R. A. Locarnini, A. V. Mishonov, J. R. Reagan, D. Seidov, E. S. Yarosh, and M. M. Zweng, 2012. World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010. Geophysical Research Letters, 39: L10603. doi:10.1029/2012GL051106.
  4. Sarmiento, J.L, Gruber, N., Brzezinski, M.A. and J.P. Dunne, 2004. High-latitude controls of thermocline nutrients and low latitude biological productivity, Nature 427, 56-60 (1 January 2004), http://dx.doi.org/10.1038/nature02127.
  5. Marinov, I., A. Gnanadesikan, J. Toggweiler, and J. L. Sarmiento, 2006, The Southern Ocean biogeochemical divide, Nature, 441, 964–967, doi:10.1038/nature04883.
  6. McNeil, B.I., and R. J. Matear, 2008. Southern Ocean acidification: A tipping point at 450-ppm atmospheric CO2. Proc. Natl. Acad. Sci., 105(48): 18860–18864.doi:10.1073/pnas.0806318105.
  7. Feely, R.A., J. Orr, V.J. Fabry, J.A. Kleypas, C.L. Sabine, and C. Landgon, 2009. Present and future changes in sea-water chemistry due to ocean acidification. In AGU Monograph on Carbon Sequestration and Its Role in the Global Carbon Cycle. Eds. B.J. McPherson, E.T. Sundquist. Am. Geophys. Union, 183, 175-188. Science